I've just joined the forum but might be able to help (and you might be able to assist me!)
I might have a drive unit available if I dismantle my aktiv Keilidhs, which I'm not using. Do you still need one?
If you replace a pair of drivers (you will not need to replace four) they need to match the frequency response and sensitivity of the units you are taking out. If they don't then it won't sound right. Firstly, you'd need to find the spec of the existing units. Linn might be able to help, but may not have retained the data. If they can't help, ask your Linn dealer or ask here. Let me know if you want a driver from me and we'll work something out.
I'm upgrading my Kabers and have changed the 015/3 tweeters for Hiquphone OW1-92, which are amazing. I'm also looking into changing the other drivers.
Can you tell me how to get the plastic front off after removing the tweeter please? This covers the screws on the mid and bass drivers on the Kabers as well as the Keilidhs.
Look forward to hearing from you.